Manufacture of lead alloys



Patented Feb. 27, 1923.

v time orrrca.

WALTHEI Z MATHESIUS, CHARLOTTENBURG, GERMANY.

MANUFACTURE OF LEAD ALLOYS.

No Drawing.

To all whom. it may concern:

Be it known that I, lVALTHER MATHESIUS, a German subject, residing in Charlottenburg, Germany, have invented a certain new and useful Improved Manufacture of Lead Alloys, of which the following is a specification.

This invention relates to the manufacture of alloys of lead with more than one or with three alkaline earth metals, calcium, barium and strontium in specified proportions.

It would be supposed that the simplest method of making alloys of four metals would be to obtain the individual metals and then to mix them together directly for producing the alloy. In the present case, however, such a method is obviously impracticable. The manufacture of the individual alkalineeart-h metals by electrolyzing their fused salts, in particular chlorides, has been successful hitherto only in the case of calcium.

It would appear to be possible to make alloys of the individual alkaline earth metals with lead by using the molten lead as the cathode in electrolyzing the fused chloride. This operation however, is unsatisfactory and uneconomical as the melting point of the chloride is so high that the difference between the melting point and the boiling point of the chloride is so small that it is practically impossible in passing the current through the molten chloride to avoid a rise of temperature towards or even up to the boiling point of the chloride. If this condition is attained not only is there a reanarkable loss of current and" other disturbance of the electrolytic operation, but the operation is accompanied by much evolution of saline vapour which is .very troublesome. I

Further consideration of the matter shows that when it is desired to introduce more than one, or all three, of the alkaline earth metals intorthe lead alloy so that all three chlorides, for instaiice'faremsedas the electrolyte, the operation becomes morefavourable as the fusing point of the mixture is,

considerably lower than that of the individual chlorides, so that the difference between melting point and vaporization point is essentially greater.

However, by this mode of working it is difiicult to obtain alloys of prescribed com- Application filed. October 21, 1922. Serial. No, 596,129.

position, for the metals pass into the lead cathode not in accordance with their proportlon in the fused electrolyte but in a proportion which depends in the first place on their order of potential. Consequently it is found that the fused electrolyte becomes impoverished in one metal and en rlched in the other metal or metals.

The present invention relates to a mode of' operation which renders it possible, in spite of the above described normal behaviour of the mixture of salts when electrolyzed, to obtain alloys of all three alkaline earth metals with lead of predetermined composition, by using a molten lead cathode.

\Vhen a mixture of fused salts in given proportions is electrolyzed with the fused lead cathode the alloy which is first produced does not correspond with the composition of the mixture of salts. After a certain time, however, there is produced a condition of equilibrium and a further impoverishment or enrichment of the salt mixture does not occur. According to the invention when this condition of equilibrium of. the molten electrolyte is'attained fresh portions of the salt mixture of predetermined composition may be-added in small portions, Whereupon the metals will separate exactly in the prescribed proportions and pass into the lead in these proportions until the aforesaid condition of equilibrium is again attained.

" At first therefore there is obtained a cathode alloy which in no way corresponds with the desired composition, but if in the course of the operation a portion of the lead cathode is continuously removed and fresh lead is substituted for that portion the composition of the cathode alloy gradually changes until that desired is attained.

The amount removed and the amount added in unit timeis in practice such as is suitable for the current strength.

When. the form of the electrolytic bath and the magnitude of the current are suitable it is possible to arrange a continuous discharging of the lead alloy and a continuous charging of the lead.

VVit-hout restricting myself to proportlons, I will state that if it is desired to produce an alloy containing lead as the major constituent, and containing equal proportions of calcium, barium and strontium, alloyed with said lead, a mixture of calcium chlori le, barium chloride and s ont um chloride Cun' taining equal amounts of the three metals,

can be used as the initial electrolyte. This mixture is fused on the lead bath which is to form the cathode, and an electric current is passed through the fused chloridesfroman insoluble anode, to the lead cathode. The current density and the voltage, can both be a little greater than those ordinarily fused in the electrolysis of fused calcium chloride.- Atfirst there is formed by electrolysis, a lead alloy containing somewhat more calcium, and somewhat less strontiumremains substantially than would correspond to equal amounts, andthe electrolysis is continued until it is found that the composition of the fused bath constant. When this condition has been reached, small additional quantities of the mixture of calcium chloride, barium chloride, and strontium ohlorilde, containing equal amounts of the three metals, are added to the bath, about as, fast 7 as the constituents of the bath are being dey composed, by the electrolytic current. At the stage, when in addition of the mixed chlorides to the bath is commenced, the lead cathode can be drawn ofi' and, a new lead cathode substituted, "after which the 1nfiow of metallic lead and the outflow of the lead alloy, can be made continuous.

. It will be obviousthat in place of starting with the mixture containing the above stated proportions of the three chlorides, it is posposition duces an alloy containing the alkaline earth v ture of the later, the error whole alloy is practically reduced to zero.

I claim l. The hereindescribed process of making lead alloys with more than one of the alkaline earth metals, by electrolysis of a fused mixture, of salts of said alkaline earth metals, in contact with a lead cathode, which comprises, first electrolyzing a mixture of fused halogen salts of such alkaline earth metals, until the'fused electrolyte has at-' tained' a condition of equilibrium in comwherein further electrolysis prometals in substantially uniform proportions to each other, and-then adding to the electrolyte, successive small portions of a mixsalts of which the electrolyte is composed, the proportion of said alkaline earth metals in such mixture being that desired in the final alloy.

2. In the manufacture referred to in claim 1, the step of substantially continuously removing a part of the molten cathode and substantially.continuously adding lead to replace the alloy so withdrawn.

3. A process of preparing lead alloys containing more than one alkaline earth metal by electrolysis of a' fused mixture of halogen salts of said alkaline earth metals, which comprises the step of adding to a fused electrolyte composed of such haloid salts, wherein electrolysis produces an alloy containing 'the said alkaline earth metals in substantially the desired proportions, successive small portionsof a mixture of the salts of which'the electrolyte is composed, the proportion of said alkaline earth metals in such mixture being that desired in the final alloy, while passing an electrolytic current through said fused mass of salts, 'while in contact with a lead cathode. In testimony whereof I have signed my name to this specification.

WALTHER MATHESIUS.

in the composition of the 

